Generatively produced turbine blade and device and method for producing same

ABSTRACT

The present invention relates to a method for producing gas turbine components, in particular aircraft turbine components, preferably low-pressure turbine blades, from a powder which is sintered selectively in layers by locally limited introduction of radiant energy, wherein the sintering is carried out in a closed first housing ( 2 ), so that a defined atmosphere can be set, wherein the powder or at least a part of the powder is generated in the same first housing ( 2 ) or in a second housing connected to the first housing in a gas-tight manner. The invention further relates to a corresponding apparatus and to a gas turbine blade produced thereby.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for producing gas turbinecomponents, in particular aircraft turbine components, preferablylow-pressure turbine blades made of a powder which is sinteredselectively in layers by locally limited introduction of radiant energy.In addition, the invention relates to an apparatus for producing gasturbine components, in particular according to a corresponding method,and also to a gas turbine blade produced thereby, in particularlow-pressure turbine blades made of a TiAl material.

2. Prior Art

What are known as rapid prototyping—or rapid manufacturing—methods, i.e.methods for rapidly producing prototypes or for rapidly producingcomponents, which utilize so-called generative production methods areknown from the prior art. In these methods, three-dimensional structuresare produced by selectively sintering powder, for example by means oflaser or electron beams which are guided over powder arranged in layers.Methods of this type have been proposed for a multiplicity of materialsand for an extremely wide variety of components, in particular alsoaircraft turbine components. Examples of this are named in DE 103 19 494A1, DE 10 2006 049 216 A1, DE 10 2004 057 865 A1, DE 10 2008 027 315 A1and DE 109 03 436 C2.

However, the methods and apparatuses described therein have variousdisadvantages. By way of example, not all the components can be producedfrom all possible materials, because the nature of the generativeproduction can introduce impurities, which lead to an unfavorableproperty profile that is unacceptable for the intended use. Particularlyin the case of titanium aluminide materials which are to be used, forexample, for low-pressure turbine blades in aircraft engines, impuritiescan lead to instances of embrittlement, which make a use in aircraftturbine construction impossible. In the worst case, the risk of theintroduction of impurities correspondingly impedes or prevents apossible use of generative production methods in the production ofturbine blades made of titanium aluminides or alloys thereof.

In addition, it must be ensured at the same time that the productionoutlay remains low in order to achieve economic production of thecomponents. Particularly in generative production methods, longprocessing times can have the effect that these can no longer be usedeconomically.

DISCLOSURE OF THE INVENTION Object of the Invention

It is an object of the present invention, therefore, to provide a methodfor producing gas turbine components, in particular aircraft turbinecomponents, preferably low-pressure turbine blades made of titaniumaluminide materials, which makes it possible to produce a correspondingcomponent with a desired property profile and at the same time iseconomical.

Technical Solution

This object is achieved by a method having the features of claim 1, anapparatus having the features of claim 8 and a gas turbine blade havingthe features of claim 9 or 10. Advantageous configurations are thesubject matter of the dependent claims.

The present invention is based on the concept that an advantageousproduction of gas turbine components, in particular aircraft turbinecomponents, such as preferably low-pressure turbine blades, made of veryreactive materials, for example titanium aluminides, can be effected ina generative production method when it can be ensured that the startingpowder used in the generative production method has an appropriatepurity. According to the invention, this is achieved by virtue of thefact that the powder production process directly precedes the generativeproduction method, i.e. selective laser or electron beam sintering, itbeing ensured that the starting powder produced is exposed to nounfavorable ambient atmosphere, which for example contains oxygen,between the powder production and the generative production of thecomponent. This avoids the situation where the powder used, i.e. forexample the very reactive titanium aluminides, can react with oxygenfrom the ambient atmosphere. This in turn has the effect that the powderparticles do not form any oxide layers, for example thin aluminum oxideor titanium oxide layers in the case of TiAl, which would then lead tothe introduction of oxygen into the component upon sintering of thepowder. Accordingly, it is provided that the powder production and thegenerative component production method are carried out in a definedatmosphere. This can be achieved if both substeps, specifically powderproduction and generative production method, are carried out in a singlehousing which can be closed in a gas-tight manner or in two housingswhich can be connected to one another in a gas-tight manner, such thatthe powder produced in the first substep no longer has to leave thedefined atmosphere before the production of the component. It is therebypossible to produce the powder in a very pure quality and to process itto form a component with a consistent purity by means of the generativeproduction method.

By avoiding exposure of the powder to an ambient atmosphere, and inparticular the avoidance of contact between the powder and oxygen orother gases in the normal ambient atmosphere and the associatedavoidance of the production of oxide layers or other reaction products,it is also possible to process very fine powder, which in conventionalproduction methods would lead to a high impurity or oxygen content ofthe component to be produced owing to its high surface area.

For the method according to the invention and a correspondingly designedapparatus, selective laser beam sintering or electron beam sintering canbe used as the generative production method.

In both methods, a plurality of radiation beams can be generated at thesame time in order to thereby ensure short process times, whichincreases the economic viability of the method. Moreover, in both typesof radiation it is possible to generate radiation with a high powerdensity, so that only short irradiation times are required for thecorresponding sintering of the powder. This too promotes the efficiencyof the method.

The method can be carried out in a vacuum or in a protective gasatmosphere or in appropriate combinations of vacuum and protective gasatmosphere. By way of example, the electron beam sintering can beeffected in a vacuum, while the powder production can be effected in aninert gas atmosphere, in order to provide, through the inert gas, acooling medium for the powder particles to be cooled for the powderproduction.

For the method, it is possible to use an extremely wide variety ofpowders, in particular different metallic powders, where the powderparticles can be formed from pure metal or from alloys. The powder canbe formed, for example, from titanium aluminide alloys or components forproducing titanium aluminide alloys, for example titanium powder,aluminum powder or powder made up of alloying constituents such asniobium or the like. In particular, a plurality of apparatuses can alsobe provided for powder production, in order to produce differentpowders. These powder production apparatuses can be provided in aplurality of separate spaces or housings or in a housing with or withoutcorresponding partitions. Possible means of transportation to the siteof the generative component production which are closed merely withrespect to the ambient atmosphere have to be ensured.

The powder can be mechanically alloyed, i.e. can be appropriatelytreated with corresponding additional powders. Moreover, a specificgrain size distribution can also be set for the powder particles.

The method according to the invention also makes it possible fordifferently alloyed powder and/or powder set differently in terms ofpowder size to be provided in different regions in the component to beproduced, so that a component with a material gradient may arise.

The powder can be produced differently by known methods. In particular,it is possible to employ atomization of a molten material, for exampleby rotary atomization.

In the case of an apparatus according to the invention, various devicesfor powder production and for generatively producing components can beprovided in a housing or in housings or spaces connected in a gas-tightmanner.

These devices comprise apparatuses for powder production by means ofatomization, for example rotary atomizers, corresponding apparatuses fortreating the powders, such as sieves and the like, an apparatus formechanical alloying, i.e. a mixer and the like, and also apparatuses forfeeding additional powder from the outside or means for storing powderin the apparatus closed in a gas-tight manner. In addition to thebeam-generating apparatus and apparatuses for guiding the beam over apowder layer, an apparatus according to the invention can moreovercomprise aids for transporting and handling the powder and also meansfor feeding gas to and for evacuating the apparatus.

In accordance with the present invention, it is therefore possible toproduce gas turbine blades, in particular low-pressure turbine bladesmade of TiAl materials, which can be formed as hollow blades with aninternal supporting structure. These components, which are producibleonly by generative methods in the case of a complicated cavitystructure, can be produced according to the invention from the materialTiAl, which is difficult to handle, or TiAl alloys, since fine-grainedpowders can be used and the production of impurities, in particular theintroduction of oxides, is prevented. Accordingly, gas turbine bladesproduced according to the invention are distinguished by a fine-grainedmicrostructure with a low degree of impurities, in particular a lowoxygen content. In addition, the gas turbine blades can have locallydifferent alloy compositions and/or possess grain size distributions.Moreover, corresponding components are distinguished by the avoidance ofsegregation, as can be observed in components produced by casting.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be illustrated on the basis of the accompanyingdrawings, which show, purely schematically, in

FIG. 1 an illustration of an apparatus for generatively producingaircraft turbine blades according to the invention; and in

FIG. 2 a perspective illustration of a turbine blade produced accordingto the invention.

EXEMPLARY EMBODIMENTS

Further advantages, characteristics and features of the presentinvention will become clear in the description of an exemplaryembodiment detailed hereinbelow.

FIG. 1 shows a purely schematic illustration of an apparatus 1 which canbe used for producing turbine blades by the method according to theinvention. The apparatus 1 has a housing 2, which surrounds two spacesor chambers 3 and 4 that are partitioned off by a partition wall (notshown in more detail) having a through-opening 15 in the housing 2. Thepowder production is effected in one space 4, while the component 27 issintered in the other space 3.

The spaces 3 and 4 each have a vacuum pump 5 and 6, such that the spaces3 and 4 can be pumped out separately from one another. Alternatively,however, provision can be made to provide merely a single pump forpumping out the entire interior of the housing 2.

In addition, provision is made of a plurality of gas feeds 7, 8, 9,which in turn make it possible to separately flood the spaces 3 and 4with gas. Here, too, provision may be made of only a single gas feed forflooding the entire interior of the housing 2. The flooding with gas canserve merely for cleaning the spaces or for setting an inert gasatmosphere.

The space 4 of the housing 2 is furthermore provided with a melt feed 10or alternatively an apparatus for melting a metal or an alloy (notshown), which comprises a nozzle device from which the melt forproducing powder can emerge. Here, it is possible to use known methods,for example rotary atomization of the melt, in order to producefine-grained powders.

The thus produced powder can be caught on a table 11, where a pushingdevice 13 can push the powder off to the side and transport it in thedirection of the space 3. In the simplest case, by way of example, thepowder situated on the table 11 can be shifted by the pushing device 13along the table 11 and the connecting plate 22 through the opening 15 inthe direction of the powder reservoir 25 in the space 3, in order to bedeposited there in the powder reservoir or on the powder reservoir as apowder layer.

The powder reservoir 25 has a double base 26, which is verticallyadjustable in accordance with the double-headed arrow, such that, at thestart of the process, the double base 26 is moved level with theconnecting plate 22 in order to receive a first powder layer.

This first powder layer is locally selectively sintered according to thecontour to be produced by an electron or laser beam 24, which isgenerated by the beam-generating device 23, the electron or laser beambeing moved over the powder layer on the double base 26. Where theelectron or laser beam impinges on the powder and melts it or starts tomelt it, the powder is locally sintered together so that a component 27is produced. Then, the double base 26 is lowered by a specific height inorder to make it possible that the pusher 13 can apply a new powderlayer. This powder layer is then correspondingly sintered again by theradiation beams 24 of the laser or electron radiation, and the processis continued until the component 27 to be produced is finished. Thecomponent 27 is then situated in a powder bed 28, which is accommodatedin the powder reservoir 25. The finished component 27 can be removedfrom there and can be removed from the housing 2 through an opening 29.

If a specific powder size is to be selected, an opening 21 can be openedin the connecting plate 22 or the table 11, such that the powder 12passes into a funnel 16 with a sieve 17, through which, however, onlythe powder having the specific powder size can pass. The powder is thencaptured in a powder reservoir 18 having a double base 19, which canthen be raised in the region of an opening 30 in the connecting plate 22such that the powder located in the powder reservoir 18 can be raised bymeans of the double base 19 into the plane of the table 11 or of theconnecting plate 22, where it can be shifted by the pusher 13 in thedirection of the powder reservoir 25. To this end, provision is made ofa hydraulic lifting apparatus 20, which can move the powder reservoir 18upward, as indicated by the double-headed arrow.

In addition, a charging funnel 14 with a lock, through which additionalpowder which has been produced externally can be introduced into theapparatus, is provided opposite the opening 30. A gas feed 8 can beconnected to the lock in order, for example, to introduce inert gas intothe lock region. Similarly, an appropriate vacuum pump (not shown) canbe provided in the region of the lock of the inlet funnel 14.

The additional powder which can be introduced into the apparatus 1 byway of the charging funnel 14 can provide for mechanical alloying of thepowder, in that alloying constituents are fed from the outside, forexample.

In addition, it is also possible to provide powder stores, for examplein the space 4 of the housing 2, in which different powders are stored,in order to then mechanically alloy these in a powder mixing apparatus(not shown) in order to thereby be able to produce desired compositionsof the powder. Moreover, further apparatuses for powder production andappropriate spaces can be provided.

For the mixing of various powders, both powders of differing chemicalcomposition and also powders of differing grain sizes can be mixed oralloyed.

In this respect, it is not only possible with the apparatus 1 presentedto process melts of alloys directly to powders and to use these in thegenerative production method, but rather it is also possible to realizemechanical alloying of powders of differing grain sizes and/or grainsize distributions and also chemical compositions in the apparatus 1.

In particular, it is thereby possible to provide powders which differ inlayers, and to thus set gradients in terms of the composition and/or ofthe grain size in the component 27 to be produced.

The gas feeds 7, 8, 9 and the pumps 5, 6 make it possible to set definedatmospheric conditions in the spaces 3 and 4 of the housing 2, in whichcase it is also possible to set different atmospheres in the spaces 3and 4. Thus, in addition to vacuum conditions, it is also possible tocreate atmospheres with defined gas compositions, for example inert gasatmospheres. In particular, it is possible to set a technicallysubstantially oxygen-free atmosphere in the housing 2, so that thecomponent 27 is not contaminated with undesired oxygen fractions.However, other gases, such as nitrogen, which could lead to theformation of nitrides can also be appropriately excluded, if working ina vacuum or inert gas atmospheres for example.

By setting the atmosphere in a defined manner, it is therefore possibleto avoid the presence of impurities in the component produced. At thesame time, by using multi-beam devices, i.e. beam-generating apparatusessuch as laser or electron beam apparatuses, which can generate aplurality of radiation beams or have high radiation powers, it ispossible to achieve a high introduction of energy into the powder, suchthat the sintering can be realized in very short process times.Accordingly, the method according to the invention can be carried outvery efficiently.

In particular, the apparatus and the corresponding method can be usedfor producing gas turbine blades made of titanium aluminide materials oralloys thereof. Furthermore, it is possible to economically producehollow blades having complicated cavities, such as cooling ducts, orcavities having complicated supporting structures.

Appropriate grain sizes can be set in the components. Segregation in thecase of alloys can also be avoided, and moreover it is possible toproduce graduated components having defined compositions in differentregions of the blade.

FIG. 2 shows an example of a low-pressure turbine blade for an aircraftturbine made of a titanium aluminide material, wherein the blade 50 hasa blade root 55 and a hollow main blade part 51. The cavity 52 of themain blade part 51 is interrupted by reinforcements 53 and 54, which areshown by dashed lines. The reinforcements divide the cavity 52 intopartial cavities 56, 57 and 58.

Owing to the method according to the invention, the main blade part 51can have different compositions in terms of the chemical compositionand/or of the grain size distribution, for example in the regions of thepartial cavities 56, 57 and 58. The change in the composition can beeffected here continuously or gradually, so that a stepless or steppedgradient is established.

Although the present invention has been described in detail withreference to the accompanying examples, it is obvious to a personskilled in the art that the invention is not limited to these examples,but rather that modifications are possible in such a manner thatdifferent combinations of the features presented are possible or thatindividual features can be omitted, without departing from the scope ofprotection of the accompanying claims.

1.-10. (canceled)
 11. A method for producing a gas turbine component,wherein the method comprises producing the component from a powder whichis sintered selectively in layers by locally limited introduction ofradiant energy, and wherein the sintering is carried out in a closed,first housing so that a defined atmosphere can be set, and the powder orat least a part of the powder is produced in the same first housing orin a second housing connected to the first housing in a gas-tightmanner.
 12. The method of claim 11, wherein the sintering is effected bya laser beam or an electron beam.
 13. The method of claim 11, wherein aplurality of radiation beams for introducing radiant energy are used atthe same time for sintering.
 14. The method of claim 11, wherein asubstantially oxygen-free atmosphere or a vacuum is set.
 15. The methodof claim 11, wherein a metallic powder is used.
 16. The method of claim11, wherein a powder of TiAl alloy or a powder for producing a TiAlalloy is used.
 17. The method of claim 11, wherein the powder ismechanically alloyed and/or a particle size distribution thereof is set.18. The method of claim 11, wherein differently alloyed powder and/orpowder set in terms of powder size is sintered in different regions ofthe component.
 19. The method of claim 11, wherein the powder isproduced by atomization.
 20. An apparatus for producing a gas turbinecomponent, wherein the apparatus comprises a first housing in whichthere are arranged (i) a reservoir for a powder bed and (ii) a radiationsource for generating at least one radiation beam for introducingradiant energy into the powder bed and (iii) an arrangement for applyingthin powder layers to the powder bed, and wherein a device for producingpowder is also arranged in the first housing or is arranged in a secondhousing that is connected to the first housing in a gas-tight manner.21. A gas turbine blade, wherein the blade is formed as a hollow bladewith an internal supporting structure.
 22. The turbine blade of claim21, wherein the blade is a low-pressure turbine blade made of a TiAlmaterial.
 23. The turbine blade of claim 21, wherein the blade is madeby a method which comprises producing the blade from a powder which issintered selectively in layers by locally limited introduction ofradiant energy, and wherein the sintering is carried out in a closed,first housing so that a defined atmosphere can be set, and the powder orat least a part of the powder is produced in the same first housing orin a second housing connected to the first housing in a gas-tightmanner.
 24. The turbine blade of claim 23, wherein the blade is alow-pressure turbine blade made of a TiAl material.
 25. The blade ofclaim 21, wherein the blade exhibits at least one of a fine-grainedmicrostructure in which 95% of grains have a grain size of less than 100nm, a locally differing alloy composition, and a locally differing grainsize distribution.
 26. The blade of claim 22, wherein the blade exhibitsat least one of a fine-grained microstructure in which 95% of grainshave a grain size of less than 100 nm, a locally differing alloycomposition, and a locally differing grain size distribution.
 27. Theblade of claim 23, wherein the blade exhibits at least one of afine-grained microstructure in which 95% of grains have a grain size ofless than 100 nm, a locally differing alloy composition, and a locallydiffering grain size distribution.
 28. The The blade of claim 24,wherein the blade exhibits at least one of a fine-grained microstructurein which 95% of grains have a grain size of less than 100 nm, a locallydiffering alloy composition, and a locally differing grain sizedistribution.